What VoIP software is this?

I know we all have once called a tech support scam company before to hear this but I cant figure out which software they use. When you call in, right before you hear the scammer a pop noise occurs. A similar noise would be a bubble popping or a Skype noise maybe. Anyone know what it is?

It could be skype. I know Microsoft has Skype for Business but i dont know if you need their software or you can setup your own VoIP server

@LoneStar_Shame#25908

vonage